Question: Which disease is most prevalent?
Paraphrase: What is the most common disease?
SPARQL (Wikidata): select ?ent where { ?ent wdt:P31 wd:Q12136 . ?ent wdt:P1193 ?obj . ?ent wdt:P31 wd:Q12136 } ORDER BY DESC(?obj)LIMIT 5 
Answer: tension headache, lactose intolerance, lactose intolerance, febrile seizure, migraine-associated vertigo